1. Field of the Invention
This invention relates generally to deposition technologies in integrated circuit chip processing and more particularly to the deposition of silicon nitride films.
2. Discussion of Related Art
The manufacture of semiconductor integrated circuits generally involves the formation of a plurality of layers of material on a semiconductor (e.g., silicon) wafer, each layer serving specific functions generally related to the routing and isolating of specific signals. One or more of these layers may comprise silicon nitride (Si3N4) as an insulator or mask. A conventional method of forming a silicon nitride layer on a wafer involves locating the wafer on a susceptor within a processing chamber and introducing a mixture of gases such as a silicon source gas, a nitrogen source gas, and a carrier gas into the processing chamber. The gases combine in the processing chamber at generally a pressure of about 300 millitorr (mTorr) to form the silicon nitride layer or film.
The processing chamber is heated by a heat source such as external heat lamps that direct light through transparent walls of the semiconductor processing a chamber to heat the chamber. A temperature measurement device such as a thermocouple, pyrometer, or a thermal camera may be used for detecting a temperature at a location on the susceptor.
The deposition rate, thickness, and uniformity of the silicon nitride layer may depend on a variety of parameters such as the pressure or the temperature in the chamber, or the amount and type of gas and flow rate of the gas across the wafer introduced into a chamber. Additionally, increasing one parameter such as temperature may affect another parameter such as pressure. For example, using a higher temperature generally allows for a lower pressure (e.g., 300 mTorr) to be used. Although higher temperatures result in a higher deposition rate of the silicon nitride layer on a wafer, high temperature deposition has its disadvantages. One disadvantage is that high temperature processing causes outdiffusion of dopants from, for example, P-type conductivity or N-type conductivity regions (P- or N-doped regions) of a semiconductor wafer. Outdiffusion may result in the breakdown of the electrical elements (e.g., transistors, capacitor, diodes, etc.) that are formed from doped regions. Avoidance of such outdiffusion is particularly important as device dimensions decrease below 0.25 xcexcm.
It is desirable to provide a method of increasing the deposition of a silicon nitride layer on a wafer while avoiding the negative consequences seen in the prior art.
Methods and apparatuses of forming a silicon nitride layer on a semiconductor wafer are disclosed. In one embodiment of the invention, a mixture of gases that include a carrier gas, a nitrogen source gas, and a silicon source gas are introduced into the processing chamber at a pressure of approximately in the range of 100 to 500 Torr to form a Si3N4 film on a wafer in the processing chamber. In another embodiment of the invention a silicon nitride film is formed using an annular-shaped pumping plate that has a sidewall with a plurality of gas holes that communicate with a pumping channel to introduce the reactants into the chamber. Other aspects and methods of the invention as well as apparatuses formed using these methods are described further below in conjunction with the following figures.